Variable capacity compressor and starting method thereof

ABSTRACT

A variable capacity compressor and a starting method thereof. The variable capacity compressor includes a four-way valve having a suction gas distribution function and an idling chamber high-pressure injection function, thereby achieving a reduced manufacturing cost and an improved reliability incurred by the use of a validated component. Further, a boosting algorithm is applicable to obtain a driving source of the four-way valve in an initial parallel pressure state. In the variable capacity compressor comprising a plurality of compression chambers having different capacities and a four-way valve to distribute a suction refrigerant gas into the plurality of compression chambers, a starting method thereof comprises determining whether the variable capacity compressor is in an initial starting mode, and controlling the four-way valve to generate a pressure difference among the plurality of compression chambers to move a piston of the four-way valve from an initial parallel pressure state if the variable capacity compressor is determined to be in the initial starting mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2005-15950, filed on Feb. 25, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to a variable capacity compressor, and more particularly, to a variable capacity compressor which includes a four-way valve having a suction gas distribution function and a high-pressure injection function, and is designed to gain a driving source of the four-way valve in an initial parallel pressure state. The present general inventive concept further relates to a starting method of the variable capacity compressor.

2. Description of the Related Art

Cooling systems designed to cool an enclosed surrounding space using a refrigeration cycle, such as air conditioners and refrigerators, include a compressor to compress a refrigerant that circulates in a closed circuit of the refrigeration cycle. A cooling capability of the cooling systems is determined depending on a compression capacity of the compressor.

Variable capacity compressors that are capable of varying the compression capacity used to compress the refrigerant have been used to perform optimum cooling consistent with a need to conserve energy by varying the cooling ability thereof.

An example of the variable capacity compressors is disclosed in Korean Patent Application No. 2002-61462 filed by the applicant of the present general inventive concept. The disclosed variable capacity compressor is designed such that only one of two compression chambers having different compression capacities selectively performs a compression operation.

The variable capacity compressor of the above Korean patent application includes an eccentric device that causes a roller, disposed in an associated one of the compression chambers, to be eccentrically rotated or to be released from its eccentrically rotated position depending on a change of a rotational direction of a rotary shaft in the associated compression chamber, thereby selectively performing a compression or compression-removal operation. The eccentric device includes two eccentric cams provided at an outer circumference of the rotary shaft in the respective compression chambers, two eccentric bushes rotatably coupled, respectively, to outer circumferences of the two eccentric cams, two rollers rotatably coupled, respectively, to outer circumferences of the two eccentric bushes, and a latch pin to latch one of the two eccentric bushes to its eccentric position and the other one to its non-eccentric position during rotation of the rotary shaft. The eccentric device further includes radially reciprocatable vanes disposed in the compression chambers, respectively, to divide an interior of the respective compression chambers into a suction space and a discharge space.

With the variable capacity compressor configured as described above, one of the compression chambers having different capacities performs an idling operation when the other compression chamber performs a compression operation according to operation of the eccentric device, thereby enabling a variable capacity operation of the compressor as a result of changing a rotational direction of the rotary shaft.

The above described variable capacity compressor is easy to install in an air conditioner because of its simplified structure having a suction gas distribution device that is directly attached to the compressor. However, the design and manufacture of the separate distribution device results in the use of an un-validated component, thereby deteriorating a reliability of the compressor.

Further, the roller of the compression chamber having no source of a refrigerant, i.e., an idling compression chamber, continuously rotates along with the rotary shaft, thereby generating a negative pressure in the idling compression chamber due to a pressure difference between the idling compression chamber and an interior of a hermetic casing of the compressor. The negative pressure hinders a rotation of the rotary shaft, resulting in a deterioration in an operational efficiency of the compressor due to power loss.

In order to solve the above problem, it is necessary to provide a separate control device to inject a high-pressure refrigerant to an idling portion of the compressor to equalize the interior pressure and a discharge pressure of the idling compression chamber. However, this increases manufacturing costs.

SUMMARY OF THE INVENTION

The present general inventive concept provides a variable capacity compressor including a four-way valve having a suction gas distribution function and an idling chamber high-pressure injection function, thereby achieving a low manufacturing cost and a high reliability due to the use of a validated component.

The present general inventive concept also provides a starting method of a variable capacity compressor that performs a boosting algorithm to obtain a driving source of a four-way valve in an initial parallel pressure state to produce a pressure difference to move a piston of the four-way valve.

Additional aspects and/or advantages of the general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.

The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing a variable capacity compressor comprising a plurality of compression chambers having different capacities, a passage switching device to supply a refrigerant gas into one of the plurality of compression chambers to perform a compression operation and to supply a compressed high-pressure refrigerant into a non-operating one of the plurality of compression chambers.

The passage switching device may be a four-way valve to distribute a gas into an operating compression chamber and to inject the compressed high-pressure refrigerant into the non-operating compression chamber.

The four-way valve may be connected to a bypass pipe branched from an outlet pipe through which the compressed high-pressure refrigerant is discharged, an inlet pipe through which a suction refrigerant gas to be compressed is supplied, and a plurality of suction pipes through which the suction refrigerant gas from the inlet pipe is delivered to the plurality of compression chambers, and the four way valve selectively connects one of the suction pipes with the inlet pipe and another one of the suction pipes with the bypass pipe.

The compressor may further comprise a control unit to control a boosting operation to move a piston of the four-way valve into an initial parallel pressure state.

The foregoing and/or other aspects and advantages of the present general inventive concept are also achieved by providing a starting method of a variable capacity compressor including a plurality of compression chambers having different capacities and a four-way valve to selectively distribute a refrigerant gas into the plurality of compression chambers, the method comprising determining whether the variable capacity compressor is in an initial starting mode, and controlling the four-way valve to generate a pressure difference to move a piston of the four-way valve in an initial parallel pressure state if the variable capacity compressor is determined to be in the initial starting mode.

The controlling of the four-way valve to generate the pressure difference may comprise operating one or more of the plurality of compression chambers and successively operating one or more remaining compression chambers after a lapse of a predetermined waiting time.

The one or more of the plurality of compression chambers or the one or more remaining compression chambers may be selectively operated for a predetermined operation time, and all of the plurality of compression chambers may be stopped from operating during the predetermined waiting time.

The method may further comprise determining whether the variable capacity compressor is in an intermittent operation mode.

If the compressor is in the intermittent operation mode, the four-way valve may be controlled to generate the pressure difference to move the piston of the four-way valve, and the variable capacity compressor may restart operation after a lapse of a predetermined rest time in the intermittent operation mode.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the exemplary embodiments of the general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a vertical sectional view illustrating a variable capacity compressor according an embodiment of the present general inventive concept;

FIG. 2 is a schematic diagram illustrating a refrigeration cycle of the variable capacity compressor of FIG. 1;

FIG. 3 is a sectional view illustrating an operational state of a four-way valve to permit a compression operation of a first compression chamber included in the variable capacity compressor of FIG. 1;

FIG. 4 is a sectional view illustrating another operational state of a four-way valve to permit a compression operation of a second compression chamber included in the variable capacity compressor of FIG. 1;

FIG. 5 is a control block diagram illustrating a starting system of the variable capacity compressor of FIG. 1 according to an embodiment of the present general inventive concept; and

FIG. 6 is a flow chart illustrating an operational sequence of a starting method of the variable capacity compressor of FIG. 1 according to an embodiment of the present general inventive concept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present general inventive concept by referring to the figures.

FIG. 1 is a vertical sectional view illustrating a variable capacity compressor 10 according to an embodiment of the present general inventive concept.

Referring to FIG. 1, the variable capacity compressor 10 includes a cylindrical hermetic casing 110 to house some of the components of the variable capacity compressor 10 including a driving unit 120 to generate a rotational power and a compressing unit 130 to compress a refrigerant upon receiving the power from the driving unit 120.

The driving unit 120 includes a cylindrical stator 121 fixed on an inner circumference of the hermetic casing 110 and a rotor 122 rotatably disposed in the stator 121 through which a rotary shaft 123 is inserted at a hollow center portion thereof. The driving unit 120 rotates the rotary shaft 123 in a forward or reverse direction.

The compressing unit 130 includes an upper first cylinder 131 and a lower second cylinder 132 that are axially stacked in parallel and define first and second compression chambers 131 a and 132 a having different compression capacities, respectively. For example, the first compression chamber 131 a may have a capacity of 100% and the second compression chamber 132 a may have a capacity of 40%. Other compression capacities may alternatively be used which provide the purposes intended, as described herein. The compressing unit 130 further includes upper and lower flanges 133 and 134 to close an upper end of the first compression chamber 131 a and a lower end of the second compression chamber 132 a, respectively. A partition 135 is interposed between the first and second compression chambers 131 a and 132 a to separate them from each other.

A first suction pipe 72 a is connected to a lateral side of the first cylinder 131 to direct a low-pressure refrigerant, delivered via an inlet pipe 70, to the first compression chamber 131 a. A second suction pipe 72 b is connected to a lateral side of the second cylinder 132 (i.e., on the same side of the compressing unit 130 as the first suction pipe 72 a) to direct the low-pressure refrigerant to the second compression chamber 132 a.

First and second eccentric units 123 a and 123 b are disposed on the rotary shaft 123 such that they are eccentrically rotatable in the first and second compression chambers 131 a and 132 a, respectively. First and second rollers 136 a and 136 b are rotatably coupled to outer circumferences of the first and second eccentric units 123 a and 123 b, respectively.

Although not shown, each of the compression chambers 131 a and 132 a may have a vane that is elastically supported at an end thereof by an outer circumference of the roller 136 a or 136 b, and is adapted to divide an interior of the compression chambers 131 a and 132 a into a refrigerant suction space and a refrigerant discharge space.

An outlet pipe 71 is disposed at an upper end of the hermetic casing 110 to discharge a compressed refrigerant from the variable capacity compressor 10.

The variable capacity compressor 10 according to the embodiment of FIG. 1 achieves a compression capacity variation by allowing a refrigerant to be compressed in one of the first and second compression chambers 131 a and 132 a having different capacities. Accordingly, the variable capacity compressor 10 includes a channel switching device to selectively connect the inlet pipe 70 with either the first suction pipe 72 a or second suction pipe 72 b.

The channel switching device is designed to return part of a compressed high-pressure refrigerant, discharged from the outlet pipe 71, into one of the first or second compression chambers 131 a or 132 a having no source of a refrigerant, in order to prevent a negative pressure from being generated in the corresponding compression chamber 131 a or 132 a.

The channel switching device may be a four-way valve 60 that may be operated by a solenoid. A bypass pipe 73 is connected between a certain position of the outlet pipe 71 and the four-way valve 60 to direct part of the compressed high-pressure refrigerant, discharged from the outlet pipe 71, into the four-way valve 60.

FIG. 2 is a schematic diagram illustrating a refrigeration cycle using the variable capacity compressor 10 according to FIG. 1.

Referring to FIG. 2, the refrigeration cycle includes the variable capacity compressor 10, a condenser 20 to cool a high-pressure, high-temperature refrigerant gas compressed by the variable capacity compressor 10, an expander 30 to decompress the refrigerant received from the condenser 20, and an evaporator 40 to evaporate the decompressed refrigerant from the expander 30 through heat absorption.

FIGS. 3 and 4 are sectional views illustrating different operational states of the four-way valve 60. FIG. 3 illustrates a first operational state that permits a compression operation of the first compression chamber 131 a, and FIG. 4 illustrates a second operational state that permits a compression operation of the second compression chamber 132 a.

Referring to FIGS. 3 and 4, the four-way valve 60 includes a body 61, a solenoid 62, a piston 63, and a channel switching member 64. The body 61 has four ports including an inlet port 61 a connected to the inlet pipe 70, a first suction port 61 b connected to the first suction pipe 72 a, a second suction port 61 c connected to the second suction pipe 72 b, and a bypass port 61 d connected to the bypass pipe 73. The solenoid 62 is installed in a lateral region of the body 61 to generate a magnetic field using a source of electric power. The piston 63 is reciprocally movable according to the magnetic field generated by the solenoid 62. The channel switching member 64 is connected to the piston 63 to reciprocally move along with the piston 63, thereby connecting each of the bypass pipe 73 and the inlet pipe 70 with one of the first suction pipe 72 a and the second suction pipe 72 b.

Depending on a position of the channel switching member 64, the four-way valve 60 simultaneously performs both a suction gas distribution function to supply a suction refrigerant gas into one of the first and second compression chambers 131 a or 132 a for compression therein via the inlet pipe 70, and a high-pressure refrigerant injection function to supply a compressed high-pressure refrigerant gas into the other one of the first and second compression chambers 131 a and 132 a having no source of the suction refrigerant gas (i.e., an idling chamber) via the bypass pipe 73.

In the first operational state in which no electric power is applied to the solenoid 62, as illustrated in FIG. 3, the channel switching member 64 is positioned to connect the inlet pipe 70 with the first suction pipe 72 a and the bypass pipe 73 with the second suction pipe 72 b.

Since the first suction pipe 72 a leads into the first compression chamber 131 a, a low-pressure refrigerant, delivered from the evaporator 40 (see FIG. 2), is introduced into and compressed in the first compression chamber 131 a (see FIGS. 1 and 2), thereby causing the variable capacity compressor 10 (see FIGS. 1 and 2) to operate with a capacity corresponding to that of the first compression chamber 131 a (for example, a full load capacity of 100%). Similarly, since the second suction pipe 72 b leads into the second compression chamber 132 a, part of a compressed high-pressure refrigerant, discharged from the outlet pipe 71, is introduced into the second compression chamber 132 a, thereby preventing generation of a negative pressure in the second compression chamber 132 a.

When electric power is applied to the solenoid 62, in the second operational state as illustrated in FIG. 4, the channel switching member 64 is positioned to connect the inlet pipe 70 with the second suction pipe 72 b and the bypass pipe 73 with the first suction pipe 72 a.

Thus, a low-pressure refrigerant, delivered from the evaporator 40, is introduced into and compressed in the second compression chamber 132 a, thereby causing the variable capacity compressor 10 to operate with a capacity corresponding to that of the second compression chamber 132 a (for example, a partial load capacity of 40%). In this case, part of a compressed high-pressure refrigerant, discharged from the outlet pipe 71, is introduced into the first compression chamber 131 a, thereby preventing generation of a negative pressure in the first compression chamber 131 a.

FIG. 5 is a control block diagram illustrating a starting system of the variable capacity compressor 10 of FIG. 1 according to an embodiment of the present general inventive concept. The starting system includes a signal input unit 200, a temperature sensor unit 210, a control unit 220, a compressor drive unit 230, an operational state sensor unit 240, and a four-way valve drive unit 250.

The signal input unit 200 inputs operational information, such as a preset temperature Ts and an operation mode selected by a user. The temperature sensor unit 210 senses an indoor temperature Tr if the variable capacity compressor 10 of the present general inventive concept is applied to an air conditioner. If the variable capacity compressor 10 is applied to a refrigerator, the temperature sensor unit 210 senses an interior temperature Tr of the refrigerator.

The control unit 220 is a microcomputer to perform a boosting algorithm to obtain a driving source of the four-way valve 60 in an initial starting operation (i.e. cold starting) or intermittent starting operation (i.e. re-starting after the lapse of a predetermined rest time) of the variable capacity compressor 10. Here, the boosting algorithm is an algorithm to generate a pressure difference sufficient to move the piston 63 (see FIGS. 3 and 4) of the four-way valve 60 in an initial parallel pressure condition. The control unit 220 has a timer that counts an operation time or rest time of the first and second compression chambers 131 a and 132 a.

The control unit 220 also compares the indoor temperature Tr with a preset temperature Ts and controls operations of the first and second compression chambers 131 a and 132 a (see FIGS. 1 and 2) based on a result of the comparison. When a temperature difference Tr−Ts is small, the control unit 220 controls a compression operation of the second compression chamber 132 a at a low operation capacity, and when the temperature difference Tr−Ts is large, the control unit 220 controls a compression operation of the first compression chamber 131 a at a high operation capacity.

The compressor drive unit 230 rotates the rotary shaft 123 (see FIG. 1) in a forward or reverse direction depending on a compressor control signal received from the control unit 220 to independently operate the first and second compression chambers 131 a and 132 a. The operational state sensor unit 240 senses an operational state of the variable capacity compressor 10 and inputs the sensed operational state to the control unit 220 to allow the control unit 220 to determine whether the variable capacity compressor 10 is in cold/hot starting operation or continuous/intermittent starting operation.

Alternatively, the control unit 220 may itself be designed to sense the operational state of the variable capacity compressor 10.

The four-way valve drive unit 250 turns on/off the four-way valve 60 so that, depending on a valve control signal received from the control unit 220, the four-way valve 60 distributes a suction refrigerant gas delivered from the evaporator 40 (see FIG. 2) into one of the first and second compression chambers 131 a and 132 a for compression and simultaneously returns part of a compressed high-pressure refrigerant into the other one of the first and second compression chambers 131 a and 132 a having no source of the suction refrigerant gas (i.e. an idling chamber of the variable capacity compressor 10).

Hereinafter, an operational sequence of a starting method of the variable capacity compressor 10 is described.

FIG. 6 is a flow chart illustrating the operational sequence of the starting method of the variable capacity compressor 10 according to an embodiment of the present general inventive concept. The starting method of FIG. 6 is described with reference to the starting system of FIG. 5.

In the variable capacity compressor 10, the first compression chamber 131 a (see FIGS. 1 and 2) has a large compression capacity of 100% and the second compression chamber 132 a has a small compression capacity of 40%. The four-way valve 60 (see FIGS. 1 and 2) is attached to the variable capacity compressor 10 to distribute a suction gas into one of the compression chambers and inject a compressed refrigerant gas into an idling chamber of the variable capacity compressor 10.

When the variable capacity compressor 10 starts to operate, the control unit 220 determines whether the variable capacity compressor 10 is in a cold or hot starting operation at operation S300.

The cold starting operation refers to an initial starting operation of the variable capacity compressor 10, and the hot starting operation is a concept opposite to the cold starting operation and is a non-initial starting operation of the variable capacity compressor 10.

If the variable capacity compressor 10 is in the hot starting operation, the control unit 220 determines whether the variable capacity compressor 10 is in a continuous or intermittent operation at operation S310.

The continuous operation is a case in which the variable capacity compressor 10 restarts operation within a predetermined rest time of approximately 15 seconds, and the intermittent operation is a case in which the variable capacity compressor 10 restarts operation after the predetermined rest time of approximately 15 seconds has lapsed.

If the variable capacity compressor 10 is in the intermittent operation, the four-way valve 60 performs a boosting algorithm to generate a pressure difference between the first compression chamber 131 a (see FIGS. 1 and 2) and the second compression chamber 132 a (see FIGS. 1 and 2) to move the piston 63 of the four-way valve 60 according to the following procedure.

First, the control unit 220 controls an operation capacity of the variable capacity compressor 10 to a full load compression capacity of 100% by operating the first compression chamber 131 a of the variable capacity compressor 10 via the compressor drive unit 230 at operation S320.

After the variable capacity compressor 10 reaches the full load compression capacity, the control unit 220 monitors an operation time of the first compression chamber 131 a to determine whether a first predetermined operation time t1 of approximately 1 minute passes) at operation S330. If the first predetermined operation time t1 passes, the operation of the first compression chamber 131 a is stopped at operation S340.

The control unit 220 then monitors a rest time of the first compression chamber 131 a to determine whether a second predetermined rest time t2 of approximately 15 seconds passes at operation S350. Here, the second predetermined rest time t2 corresponds to a time required to convert to a non-operating compression chamber. If the second predetermined rest time t2 passes, the control unit 220 controls the operation capacity of the variable capacity compressor 10 to a partial load capacity of 40% by operating the second compression chamber 132 a via the compressor drive unit 230 at operation S360.

After the variable capacity compressor 10 reaches the partial load capacity, the control unit 220 monitors an operation time of the second compression chamber 132 a to determine whether a third predetermined operation time t3 of approximately 1 minute passes at operation S370. If the third predetermined operation time t3 passes, the operation of the second compression chamber 132 a is stopped at operation S380.

The third predetermined operation time t3 may be set to be equal to or different from the first predetermined operation time t1 of the first compression chamber 131 a and may be varied according to the capacity of the variable capacity compressor 10.

If it is determined at the operation S300 that the variable capacity compressor 10 is in the cold starting operation, i,e. in an initial starting, the control unit 220 proceeds to the operation S320 to enable the four-way valve 60 to perform the boosting algorithm, in order to generate a pressure difference between the first compression chamber 131 a and the second compression chamber 132 a to move the piston 63 of the four-way valve 60 in an initial parallel pressure condition.

If the four-way valve 60 is movable as a result of the boosting algorithm, the control unit 220 compares an indoor temperature Tr with a preset temperature Ts and determines whether a temperature difference Tr−Ts is more than a predetermined standard temperature Ta at operation S390.

If the temperature difference Tr−Ts is more than the predetermined standard temperature Ta, the control unit 220 increases the operation capacity of the variable capacity compressor 10 to operate the first compression chamber 131 a at operation S400. If the temperature difference Tr−Ts is less than the predetermined standard temperature Ta, the control unit 220 decreases the operation capacity of the variable capacity compressor 10 to operate the second compression chamber 132 a at operation S410.

As apparent from the above description, according to a variable capacity compressor and a starting method thereof according to the present general inventive concept, a four-way valve is employed to distribute a suction refrigerant gas into one of a plurality of compression chambers of the variable capacity compressor for compression and to simultaneously inject a compressed high-pressure refrigerant gas into another compression chamber (i.e. an idling chamber of the variable capacity compressor) thereby achieving a reduced manufacturing cost and an improved reliability incurred by the use of a validated component. Further, by performing a boosting algorithm to gain a driving source of the four-way valve, it is possible to effectively generate a pressure difference sufficient to move a piston of the four-way valve from an initial parallel pressure state.

Although embodiments of the present general inventive concept have been shown and described, it should be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the claims and their equivalents. 

1. A variable capacity compressor, comprising: a plurality of compression chambers having different capacities; a passage switching device to supply a refrigerant gas into one of the plurality of compression chambers to perform a compression operation and to supply a compressed high-pressure refrigerant into a non-operating one of the plurality of compression chambers.
 2. The compressor according to claim 1, wherein the passage switching device comprises a four-way valve to distribute a gas into an operating compression chamber and to inject the compressed high-pressure refrigerant into the non-operating compression chamber.
 3. The compressor according to claim 2, wherein the four-way valve is connected to: a bypass pipe branched from an outlet pipe through which the compressed high-pressure refrigerant is discharged, an inlet pipe through which a suction refrigerant gas to be compressed is supplied, and a plurality of suction pipes through which the suction refrigerant gas from the inlet pipe to the plurality of compression chambers is delivered to the plurality of compression chambers, and the four-way valve selectively connects one of the suction pipes with the inlet pipe and another one of the suction pipes with the bypass pipe.
 4. The compressor according to claim 2, further comprising: a control unit to control a boosting operation to move a piston of the four-way valve from an initial parallel pressure state.
 5. A variable capacity compressor usable with a cooling system, comprising: a first compression chamber having a first compression capacity; a second compression chamber having a second compression capacity; and a valve unit to selectively provide uncompressed gas and compressed gas to the first and second compression chambers according to an operation mode of the variable capacity compressor.
 6. The compressor according to claim 5, wherein the valve unit provides uncompressed gas to an operating one of the first and second compression chambers and provides compressed gas to a non-operating one of the first and second compression chambers.
 7. The compressor according to claim 5, wherein the first compression capacity is a full capacity and the second compression capacity is a partial capacity.
 8. The compressor according to claim 5, wherein the valve unit comprises: a first pipe to provide gas to the first compression chamber; a second pipe to provide gas to the second compression chamber; an inlet pipe to receive the uncompressed gas from a refrigeration cycle; and a bypass pipe to receive the compressed gas from an output of the variable capacity compressor.
 9. The compressor according to claim 8, wherein the valve unit further comprises: a valve body having a passageway disposed therein to connect to the first, second, inlet, and bypass pipes; a switching member disposed in the passageway to block or connect the first, second, inlet, and bypass pipes with respect to each other; and a driving unit to move the switching member in the passageway.
 10. The compressor according to claim 9, wherein the driving unit comprises a piston and a solenoid.
 11. The compressor according to claim 8, wherein the valve unit has: a first operational state in which the first pipe is connected to the inlet pipe and blocked from the bypass pipe, and the second pipe is connected to the bypass pipe and blocked from the inlet pipe; and a second operational state in which the first pipe is connected to the bypass pipe and blocked from the inlet pipe, and the second pipe is connected to the inlet pipe and blocked from the bypass pipe.
 12. A method of starting a variable capacity compressor including a plurality of compression chambers having different compression capacities and a four-way valve to selectively distribute a cooling gas into the plurality of compression chambers, the method comprising: determining whether the variable capacity compressor is in an initial starting mode; and controlling the four-way valve to generate a pressure difference among the plurality of compression chambers to move a piston of the four-way valve from an initial parallel pressure state when the variable capacity compressor is determined to be in the initial starting mode.
 13. The method according to claim 12, wherein the controlling of the four-way valve to generate the pressure difference comprises: operating one or more of the plurality of compression chambers; resting the variable capacity compressor for a predetermined waiting time; and operating one or more remaining compression chambers after a lapse of the predetermined waiting time.
 14. The method according to claim 13, wherein the one or more of the plurality of compression chambers or the one or more remaining compression chambers are selectively operated for a predetermined operation time.
 15. The method according to claim 13, wherein all of the plurality of compression chambers are prevented from operating during the predetermined waiting time.
 16. The method according to claim 12, further comprising: determining whether the variable capacity compressor is in an intermittent operation mode.
 17. The method according to claim 16, wherein the four-way valve is controlled to generate the pressure difference among the plurality of compression chambers to move the piston of the four-way valve when the variable capacity compressor is determined to be in the intermittent operation mode.
 18. The method according to claim 16, wherein, in the intermittent operation mode, the variable capacity compressor restarts operation after a lapse of a predetermined rest time.
 19. The method according to claim 12, wherein the determining of whether the variable capacity compressor is in the initial starting mode comprises determining whether the variable capacity compressor is in a cold starting mode or a hot starting mode.
 20. The method according to claim 19, further comprising: determining whether the variable capacity compressor is in an intermittent operation mode or a continuous operation mode when it is determined that the variable capacity compressor is in the hot starting mode.
 21. The method according to claim 20, wherein the controlling of the four-way valve to generate the pressure difference among the plurality of compression chambers is performed when the variable capacity compressor is in the cold starting mode or the intermittent starting mode.
 22. The method according to claim 12, further comprising: operating a first compression chamber for a first predetermined operation time; resting the variable capacity compressor for a first predetermined rest time; and operating a second compression chamber for a second predetermined operation time.
 23. The method according to claim 22, wherein: the operating of the first compression chamber comprises operating at a 100% compression capacity for the first predetermined operation time; and the operation of the second compression chamber comprises operating at a 40% compression capacity for the second predetermined operation time. 